Medical endoscopes are used to inspect the interiors of human cavities. Such instruments include rigid endoscopes containing a lens system, flexible endoscopes containing a flexible image guiding bundle and video endoscopes.
In general, endoscopes are constructed with a diameter of only a few millimeters but are often several hundreds of millimeters long. Rigid endoscopes include an inner tube containing an optical system which relays an image of the cavity from the distal tip of the endoscope back to the proximal end of the endoscope. These endoscopes further contain an outer tube separated from the inner tube by a space filled with illumination fibers. The fibers guide externally created light into the internal cavity. The image relayed through the inner tube is observed at the proximal end by the operator. Additionally, a video camera may be utilized to capture the image.
Conventional rigid endoscopes possess a single optical viewing channel which provides a two-dimensional image of the viewing area. Endoscopes with a single optical system may, in some instances, create three-dimensional information about an object. For instance, objects at different distances may appear differently sized, while overlapping of objects indicate which object is in front and which is in the back. For many surgical endoscopic procedures this three dimensional information is sufficient and stereoscopic vision is unnecessary. However, more complex surgical procedures require a more specific reproduction of the viewing area, including a better view of the spatial relationships between objects. Many of these procedures utilize robotic assistance requiring stereo endoscopic observation for instrument control.
Stereoscopic systems in general produce two images which display an object from slightly different perspectives, i.e., a left and right image. The human brain is able to merge these two slightly different images, received from the left and right eyes, and create a three-dimensional impression. For example, DE 164944 (1904) discloses an instrument with two separate optical viewing paths which permits viewing an object from two different directions from a position opposite the distal end of the endoscope. The proximal part of the endoscope is connected to a double eyepiece which simultaneously permits viewing of the object with both eyes. DE 209083 describes an endoscope accessory which separates the exit pupil of a monoscopic visual instrument into left and right parts with slightly different perspectives. These two basic constructions are still used in most conventional stereo endoscope systems.
It is often advantageous to use a two optical endoscopic system with a larger eye base, particularly in surgical procedures involving the abdomen. Although a two optical path system provides better stereoscopic visualization, technical problems may also arise. Endoscopic optical systems may expand and contract during exposure to heat during the sterilization process. In addition, the lens system may move, resulting in shifting of the focus and magnification of the two images. Slight exposure to mechanical shock or movement can cause instrument misalignment.
What is needed in the art, therefore, is a cost effective stereo endoscope system with a larger eye base that avoids misalignment during use and sterilization. The camera utilized with the instrument should adapt to fit endoscopes with varying diameters and directions of view.